Intermediate-depth Ventilation of the Antarctic Circumpolar Current in the Southwestern Scotia Sea

西南斯科舍海南极绕极流的中深度通风

• 批准号: 0961523
• 负责人: Alejandro Orsi
• 金额: $ 39.24万
• 依托单位: Texas A&M Research Foundation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-04-15 至 2014-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0961523&HistoricalAwards=false
• 关键词: Intermediate; depth; Ventilation; Antarctic; Circumpolar

The Intermediate-depth Ventilation of the Antarctic Circumpolar Current in the Southwestern Scotia Sea project seeks answers to these climate-relevant questions: Is the export of ventilated cold waters from the Antarctic Slope Current (ASC) at the northern side of the South Scotia Ridge (SSR) sufficient to explain the observed rapid freshening and cooling of the Antarctic Circumpolar Current (ACC) downstream of Drake Passage? Where and how is Modified Circumpolar Deep Water (MCDW) injected to the deep water of the ACC? Is the proximity of the ACC to the continental slope of the SSR a critical factor in determining how much MCDW is delivered across the slope? The aim of this project in answering these question is to correctly represent the ventilation rate for the Circumpolar Deep Water (CDW) in large-scale ocean circulation models. The main goal is to identify and describe the main mechanism governing the offshore transport of ventilated upper waters from the ASC to the Scotia Sea along intermediate density layers.The guiding hypothesis for the project is that the magnitude and location of the northward injection of cold, fresh, ventilated slope water from the ASC to the deep Scotia Sea within isopycnal layers varies with the proximity of the southern boundary of the ACC to the South Scotia Ridge, and is therefore subject to considerable mesoscale variability.The specific objectives are to characterize the flow of the ASC in the southwestern Scotia Sea where it converges with the ACC, assess mechanisms for production of ventilated slope waters along the path of the ASC, determine the physical and chemical properties, and volume transport of ventilated slope waters carried along this path and their cross-slope outflows, identify the pathway(s) for their spreading and sinking into the Circumpolar Deep Water (CDW) layer of the ACC in the Scotia Sea, and determine the spatial distribution of diapycnal mixing across the ridge and the Antarctic Slope Front system, including its relationship to tides and intrusions. The hydrographic data from two well coordinated international cruises in the southwestern Scotia Sea, and the one-year time series of current, salinity and temperature measurements from three moorings deployed across the northern slope of the SSR, will be analyzed and synthesized with all historical and complementary data sets relevant to the objectives of this project.Intellectual Merit: The proposed analysis will determine the importance of direct ventilation of the deep ACC in the Scotia Sea relative to indirect ventilation through upward mixing of bottom trapped outflows of denser bottom waters. By better constraining mechanisms by which climate related changes in the cold Antarctic coastal waters can rapidly impact the rest of the World Ocean, this analysis will improve our ability to model deep ocean ventilation. The first long-term moorings from this critical interface region between the Weddell Sea and the Global Ocean will add to the regional database with current, temperature and salinity profile measurements that resolve the small cross-slope scales associated with the hypothesized ventilation mechanism. It builds on an earlier international experiment (DOVETAIL: 1997-2000) and is coordinated with a Spanish research program. Broader Impacts: This research project provides an extraordinary opportunity to foster international collaboration with South American and European investigators involved in concurrent regional field programs. Two Ph.D. students will be supported by this grant, and will assimilate data collected in this program into their research projects. Project documentation and results publication will contribute to the US component of the IPY SASSI research program (http://sassi.tamu.edu). All data from this program will be quality controlled, submitted to NODC and added to the Southern Ocean Database disseminated to the broader community online at http://woceSOatlas.tamu.edu.This project is a contribution to the U.S. CLIVAR (CLImate VARiability and predictability) program.

西南斯科舍海南极绕极流中深度通风项目寻求这些与气候有关的问题的答案：从南斯科舍海脊(SSR)北侧的南极坡流(ASC)输出的通风冷水是否足以解释在Drake Passage下游观察到的南极绕极流(ACC)的快速清新和冷却？改良环极深水(MCDW)在哪里以及如何注入ACC的深水？Acc是否接近SSR的大陆斜坡，这是决定通过斜坡输送多少MCDW的关键因素？这个项目回答这些问题的目的是为了在大尺度海洋环流模式中正确地表示绕极深水(CDW)的通气率。该项目的主要目标是确定和描述控制通风上层水沿着中等密度层从ASC到斯科舍海的离岸输送的主要机制。该项目的指导假设是，在等密度层内从ASC向北向Scotia海深处注入冷的、新鲜的、通风的斜坡水的大小和位置随着ACC的南部边界靠近南Scotia海脊而变化，因此受到相当大的中尺度变化的影响。具体目标是描述ASC在与ACC汇合的斯科舍海西南部的流动特征，评估沿着ASC路径产生通风斜坡水的机制，确定沿这条路径输送的通风坡水及其越坡出流的物理化学性质和体积输送，确定其扩散和下沉到斯科舍海ACC环极深水层的途径(S)，并确定跨脊线和南极坡锋系统的昼夜混合的空间分布，包括其与潮汐和入侵的关系。来自斯科舍海西南部两个协调良好的国际邮轮的水文数据，以及从部署在SSR北坡的三个系泊设备测量的一年的海流、盐度和温度的时间序列，将与与本项目目标相关的所有历史和补充数据集进行分析和合成。情报价值：拟议的分析将确定斯科舍海深层ACC的直接通风相对于通过更密集底水的底部困住流出的向上混合的间接通风的重要性。通过更好地约束南极寒冷沿海水域与气候有关的变化可能迅速影响世界海洋其余部分的约束机制，这一分析将提高我们模拟深海通风的能力。来自韦德尔海和全球海洋之间这一关键界面区域的第一批长期系泊将增加到区域数据库，提供海流、温度和盐度剖面测量，以解决与假设的通风机制有关的小横坡尺度。它建立在早期的国际实验(燕尾：1997-2000年)的基础上，并与西班牙的一个研究计划相协调。更广泛的影响：这一研究项目提供了一个非同寻常的机会，可以促进与同时参与区域实地项目的南美和欧洲调查人员的国际合作。两名博士生将得到这笔助学金的资助，他们将把在这个项目中收集的数据同化到他们的研究项目中。项目文件和成果出版将有助于国际和平研究所萨西研究计划(http://sassi.tamu.edu).)的美国部分该计划的所有数据都将经过质量控制，提交给国家海洋数据中心，并添加到南大洋数据库中，在http://woceSOatlas.tamu.edu.This向更广泛的社区在线传播该项目是对美国气候可变性和可预测性计划的贡献。